Regulated linear purge solenoid valve

ABSTRACT

A pressure regulator is associated with a solenoid-operated valve that is operated by a pulse waveform at a fundamental frequency substantially greater than the frequency response of the valve mechanism. This substantially attenuates solenoid pulsations and applies a predetermined pressure differential across the valve mechanism to accomplish improved flow control accuracy. The invention is especially advantageous for purging fuel vapor to an intake manifold of an internal combustion engine of an automotive vehicle.

FIELD OF THE INVENTION

[0001] This invention relates generally to emission control valves forautomotive vehicles. In one specific aspect, the invention relates tosolenoid-operated fluid valves for purging volatile fuel vapors fromfuel tanks and vapor storage canisters to internal combustion enginesthat power such vehicles.

BACKGROUND OF THE INVENTION

[0002] A known on-board evaporative emission control system comprises avapor collection canister that collects volatile fuel vapors generatedin the headspace of the fuel tank by the volatilization of liquid fuelin the tank and a canister purge solenoid (CPS) valve for periodicallypurging collected vapors to an intake manifold of the engine. The CPSvalve comprises a solenoid actuator that is under the control of amicroprocessor-based engine management system.

[0003] During conditions conducive to purging as determined by theengine management system on the basis of various inputs to it,evaporative emission space that is cooperatively defined by the tankheadspace and the canister is purged to the engine intake manifoldthrough the CPS valve, which is fluid-connected between the canister andthe engine intake manifold. The CPS valve is opened by a signal from theengine management computer in an amount that allows intake manifoldvacuum to draw volatile fuel vapors from the canister for entrainmentwith the combustible mixture passing into the engine's combustionchamber space at a rate consistent with engine operation to provide bothacceptable vehicle driveability and an acceptable level of exhaustemissions.

[0004] A known CPS valve comprises a movable valve element that isresiliently biased by a compression spring against a valve seat to closethe valve to flow when no electric current is being delivered to thesolenoid. As electric current begins to be increasingly applied to thesolenoid, increasing electromagnetic force acts in a sense tending tounseat the valve element and thereby open the valve to fluid flow. Thiselectromagnetic force must overcome various forces acting on themechanical mechanism before the valve element can begin to unseat,including overcoming both whatever static friction (stiction) is presentbetween the valve element and the seat, as well as the opposing springbias force. Once the valve element has unseated, the valve element/valveseat geometry also plays a role in defining the functional relationshipof fluid flow rate through the valve to electric current supplied to thesolenoid coil. Furthermore, the extent to which a given valve possesseshysteresis will also be reflected in the functional relationship.

[0005] When the valve element comprises a tapered pintle that isselectively positioned axially within a circular orifice which iscircumscribed by the valve seat, a well defined flow rate vs. pintleposition characteristic can be obtained. However, certain geometricfactors present at the valve element/valve seat interface may preventthis characteristic from becoming effective until the valve element hasunseated a certain minimum distance from the valve seat. Accordingly,each graph plot of fluid flow rate through the valve vs. electriccurrent supplied to the solenoid coil may be considered to comprisedistinct spans: a short initial span that occurs between valve closedposition and a certain minimum valve opening; and a more extensivesubsequent span that occurs beyond a certain minimum valve opening.

[0006] One specific type of CPS valve comprises a linear solenoid and alinear compression spring that is increasingly compressed as the valveincreasingly opens. It is sometimes referred to as a linear solenoidpurge valve, or LSPV for short. Such a valve can provide certaindesirable characteristics for flow control. By itself a linear solenoidpossesses a force vs. electric current characteristic that is basicallylinear over a certain range of current. When a linear solenoid isincorporated in an electromechanical device, such as a valve, theoverall electromechanical mechanism possesses an output vs. electriccurrent characteristic that is a function of not just the solenoid, butalso the mechanical mechanism, such as a valve mechanism, to which thesolenoid force is applied. As a consequence then, the output vs.electric current characteristic of the overall device is somewhatmodified from that of the linear solenoid alone.

[0007] While a CPS valve that incorporates both a linear solenoid and atapered pintle valve element which is selectively positionable axiallywithin a circular orifice that is circumscribed by the valve seat canexhibit a desired fluid flow rate vs. pintle position characteristic,such characteristic may not become effective until after the pintle hasopened a certain minimum amount because of geometric factors at thepintle/seat interface, as noted earlier. Accordingly, each graph plot offluid flow rate through the valve vs. electric current applied to thesolenoid coil may be considered to comprise the spans referred to above,namely, a short initial span that occurs between valve closed positionand a certain minimum valve opening, and a more extensive subsequentspan that occurs beyond a certain minimum valve opening.

[0008] Generally speaking, a linear solenoid purge valve may begraphically characterized by a series of graph plots of fluid flow ratevs. electric current, each of which is correlated to a particularpressure differential across the valve. Each graph plot may becharacterized by the aforementioned short initial span and the moreextensive subsequent span. Within the latter span of each graph plot,one especially desirable attribute is that a substantially constantrelationship between incremental change in an electric control currentapplied to the solenoid and incremental change in fluid flow ratethrough the valve may be obtained by appropriate design of the valveelement/valve seat interface geometry. Within the former span,incremental change in fluid flow rate through the valve may however beara substantially different relationship to incremental change in anelectric control current applied to the solenoid.

[0009] In one such linear solenoid purge valve, a certain minimumelectric current is required before the valve begins to open. For agiven pressure differential across the valve, a corresponding graph plotof fluid flow rate vs. electric current may be described as comprising arelatively short initial span where a small incremental change inelectric current will result in an incremental change in flow that ismuch different from the incremental change that occurs over an ensuingspan where the valve has opened beyond a certain minimum opening andincremental change in flow through the valve bears a substantiallyconstant relationship to incremental change in electric current.

[0010] Electric current to the solenoid coil of any solenoid-operateddevice can be delivered in various ways. One known way is by applying apulse width modulated D.C. voltage across the solenoid coil. In choosingthe pulse frequency of the applied voltage, consideration may be givento the frequency response characteristic of the combined solenoid andmechanical mechanism operated by the solenoid. If a pulse frequency thatis well within the frequency response range of the combined solenoid andmechanism is used, the mechanism will faithfully track the pulse widthsignal. On the other hand, if a pulse frequency that is well beyond thefrequency response range of the combined solenoid and mechanicalmechanism is used, the mechanism will be positioned according to thetime average of the applied voltage pulses. The latter technique may bepreferred over the former because the mechanical mechanism will notreciprocate at the higher frequency pulse width modulated waveform, butrather will assume a position corresponding to the time averaged currentflow in the solenoid coil. Under the former technique, the mechanismcould, by contrast, experience significant reciprocation as it tracksthe lower frequency waveform, and that might create unacceptablecharacteristics. In the case of a CPS valve, such characteristics mayinclude undesirable pulsations in the purge flow and objectionable noisecaused by repeated impacting of the valve element with the valve seatand/or a limit stop that limits maximum valve travel. Such a valve mayexperience unacceptable variation in the start-to-flow duty cycle.

[0011] In order to address the pulsation issue, it is known to associatea mechanical pressure regulator with a CPS valve. The pressure regulatormechanically damps the purge flow pulses, but does not address the rootcause, which is due to the pulsating solenoid.

[0012] Accordingly, a need exists for further improvement in certainaspects of pulse-operated emission control valves such as CPS valvesbecause such valves may be required to perform under diverse vehicleoperating conditions. For a CPS valve, purging of volatile fuel vapor tothe intake manifold when the engine is idling may be quite difficult toaccurately control.

SUMMARY OF THE INVENTION

[0013] One general aspect of the invention relates to anelectric-operated pressure-regulated fluid flow control valve comprisinga valve mechanism that is positioned within a valve body by an electriccontrol signal to control fluid flow through the valve body and that hasa frequency response characteristic which renders the valve mechanismincapable of faithfully tracking the fundamental frequency of anelectric control signal whose fundamental frequency is greater than apredetermined frequency that, when applied in control of the valvemechanism, positions the valve mechanism to a position corresponding toa most recent time average of the electric control signal free of anysignificant pulsing of the valve mechanism, and a pressure regulatorcomprising a flow path having an entrance through which fluid flow thathas passed through the valve mechanism enters the pressure regulatorflow path and an exit from which fluid flow that has entered thepressure regulator flow path exits the pressure regulator flow path, thepressure regulator comprising a pressure regulating mechanism thatregulates the pressure at the entrance of the pressure regulator flowpath to a pressure that is essentially independent of pressure at theexit of the pressure regulator flow path.

[0014] Another general aspect relates to an electric-operatedpressure-regulated fuel vapor purge valve for purging fuel vapor from afuel tank to an intake manifold of an internal combustion enginecomprising a valve mechanism that is positioned within a valve body byan electric control signal to control flow through the valve body andthat has a frequency response characteristic which renders the valvemechanism incapable of faithfully tracking the fundamental frequency ofan electric control signal whose fundamental frequency is greater than apredetermined frequency that, when applied in control of the valvemechanism, positions the valve mechanism to a position corresponding toa most recent time average of the electric control signal free of anysignificant pulsing of the valve mechanism, and a pressure regulatorcomprising a flow path having an entrance through which flow that haspassed through the valve mechanism enters the pressure regulator flowpath and an exit for communicating the pressure regulator flow path toan engine intake manifold, the pressure regulator comprising a pressureregulating mechanism that regulates the pressure at the entrance of thepressure regulator flow path to a pressure that is essentiallyindependent of intake manifold vacuum.

[0015] A further aspect relates to an LSPV, including a pressureregulator, that is believed to provide further improvements in purgeflow control accuracy over a substantial range of valve operation andunder diverse operating conditions.

[0016] A still further aspect relates to the provision of certainconstructional features in a pressure regulator that, in associationwith a CPS valve, are believed to provide improved purge flow controlaccuracy by significantly attenuating the influence of variations inpressure differential that would otherwise produce variations in thepurge for a given valve opening.

[0017] The foregoing, along with additional features, and otheradvantages and benefits of the invention, will be seen in the ensuingdescription and claims which are accompanied by drawings. The drawingsdisclose a preferred embodiment of the invention according to the bestmode contemplated at this time for carrying out the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a schematic diagram of an on-board evaporative emissioncontrol system, including an enlarged longitudinal cross-sectional viewthrough a canister purge solenoid valve.

[0019]FIG. 2 is a representative graph plot related to FIG. 1.

[0020]FIG. 3 is a longitudinal cross-sectional view through anothercanister purge solenoid valve.

[0021]FIG. 4 is a longitudinal cross-sectional view through the canisterpurge solenoid valve of FIG. 3 and an associated pressure regulator inaccordance with the inventive principles.

[0022]FIG. 5 is a series of graph plots useful in explaining theinventive principles in relation to FIG. 4.

[0023]FIG. 6 is a longitudinal view, partly in cross-section, throughanother embodiment in accordance with the inventive principles.

[0024]FIG. 7 is a longitudinal view of the embodiment of FIG. 6, buthaving a different portion in cross-section.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0025]FIG. 1 shows an evaporative emission control system 10 of a motorvehicle comprising a vapor collection canister (carbon canister) 12 anda canister purge solenoid (CPS) valve 14 connected in series between afuel tank 16 and an intake manifold 18 of an internal combustion engine20 in a known fashion. An engine management computer 22 supplies a valvecontrol signal as an input to a pulse width modulation (PWM) circuit 24to create a pulse width modulated signal which is amplified by a drivecircuit 26 and applied to electric terminals 14 et of valve 14.

[0026] Valve 14 comprises a housing 28 having an inlet port 14 i that isfluid-coupled via a conduit 30 with a purge port 12 p of canister 12 andan outlet port 14 o that is fluid-coupled via a conduit 32 with intakemanifold 18. A conduit 34 communicates a canister tank port 12 t toheadspace of fuel tank 16. An operating mechanism comprising a solenoidactuator 14 sa is disposed within housing 28 for opening and closing aninternal passage that extends between ports 14 i and 14 o. The mechanismincludes a bias spring 14 bs that acts to urge a valve element 14 veclosed against a valve seat 14 vs for closing the internal passage toflow. When the solenoid actuator is progressively energized by enginemanagement computer 22, electromagnetic force is applied to an armature14 a in opposition to the bias spring force to unseat valve element 14ve from valve seat 14 vs and thus open the internal passage so that flowcan occur between ports 26 and 30.

[0027] Canister 12 is also seen to comprise a vent port 12 v via whichthe evaporative emission space where the fuel vapors are contained isvented to atmosphere. Such venting may be via an atmospheric vent valve(not shown) that is operated closed at certain times, such as duringOBDII testing.

[0028]FIG. 2 depicts a representative control characteristic for valve14 wherein fluid flow rate through the valve is related to the dutycycle of a pulse width modulated voltage that is applied acrossterminals 14 et. A certain minimum duty cycle, about 10% in the example,is required before the valve begins to open. As the duty cycle increasesbeyond 10%, the flow rate bears a generally straight line relationshipto duty cycle. At 100% duty cycle a constant D.C. voltage is appliedacross terminals 14 et. The frequency of the pulse waveform thataccomplishes this type of operation is relatively low, a representativefrequency being within a range from about 5 Hz to about 20 Hz, butpossibly as high as about 50 Hz. For valve mechanisms whose frequencyresponse extends beyond such a range, the mechanism will experiencesignificant reciprocal motion as it follows the pulse waveform.

[0029] Because the valve is not pressure-regulated, flow rate will alsobe a function of the pressure differential across the valve ports.Temperature and voltage variations may also influence the relationship.

[0030] It is known that the use of a linear solenoid can improve controlaccuracy, and FIG. 3 shows an example of a linear solenoid purge valve14′, certain parts of which correspond to parts of valve 14 alreadymentioned, and they will be designated by corresponding primed referencenumerals.

[0031] Valve 14′ comprises a two-piece body B1, B2 having an inlet port14 i′ and an outlet port 14 o′. Valve 14′ has a longitudinal axis AX,and body piece B1 comprises a cylindrical side wall 40 that is coaxialwith axis AX and that is open at its upper axial end where it is inassembly with body piece B2. Side wall 40 comprises upper and lower sidewall-portions 40A, 40B joined by a shoulder 42; the former side wallportion is fully cylindrical while the latter is cylindrical except inthe region where it is radially intercepted by port 14 o′. Port 14 i′ isin the shape of an elbow that extends from the lower axial end of sidewall 40. By itself, body piece B1 is enclosed except for its open upperaxial end and the two ports 14 o′ and 14 i′.

[0032] A linear solenoid S is disposed in body piece B1, having beenintroduced through the open upper end of body piece B1 duringfabrication of the valve. The solenoid comprises a bobbin 44, magnetwire wound on bobbin 44 to form a bobbin-mounted electromagnetic coil46, and stator structure associated with the bobbin-coil. This statorstructure comprises an upper stator end piece 48 disposed at the upperend of the bobbin-mounted coil, a cylindrical side stator piece 50disposed circumferentially around the outside of the bobbin-mountedcoil, and a lower stator end piece 52 disposed at the lower end of thebobbin-mounted coil.

[0033] Upper stator end piece 48 includes a flat circular disk portionwhose outer perimeter fits to the upper end of side piece 50 and thatcontains a hole into which a bushing 54 is pressed so as to be coaxialwith axis AX. The disk portion also contains another hole to allow forupward passage of a pair of bobbin-mounted electrical terminals 56 towhich ends of magnet wire 46 are joined. Piece 48 further comprises acylindrical neck 58 that extends downward from the disk portion acertain distance into a central through-hole in bobbin 44 that isco-axial with axis AX. The inner surface of neck 58 is cylindrical whileits outer surface is frusto-conical so as to provide a radial thicknessthat has a progressively diminishing taper as the neck extends into thebobbin through-hole.

[0034] Lower stator end piece 52 includes a flat circular disk portionwhose outer perimeter fits to the lower end of side piece 50 and thatcontains a hole into which a bushing 60 is pressed so as to be coaxialwith axis AX. Piece 52 further comprises an upper cylindrical neck 62that extends upwardly from the disk portion a certain distance into thecentral through-hole in bobbin 44 and that is co-axial with axis AX.Neck 62 has a uniform radial thickness. Piece 52 still further comprisesa lower cylindrical neck 64 that extends downward from the disk portiona certain distance so that its lowermost end fits closely within lowerside wall portion 40B. A valve seat element 66 is necked to press-fitinto the open lower end of neck 64 and is sealed to the inside of wallportion 40B by an O-ring 67. Above the lowermost end that fits to sidewall 40, neck 64 contains several through-holes 68 that provide forcommunication between port 14 o′ and the space disposed above seatelement 66 and bounded by neck 64. Side wall 40 allows thiscommunication by not restricting through-holes 68.

[0035] Bushings 54 and 60 serve to guide a valve shaft 70 for lineartravel motion along axis AX. A central region of shaft 70 is slightlyenlarged for press-fit of a tubular armature 72 thereto. The lower endof shaft 70 comprises a valve 74 that coacts with valve seat element 66.Valve 74 comprises a head, integrally formed with shaft 70 and havingthe general shape of a tapered pintle, comprising a rounded tip 74A, afrustoconical tapered section 74B extending from tip 74A, a groovedcylindrical section 74C extending from section 74B, and an integralback-up flange 74D that in part defines the upper axial end of thegroove of section 74C. An O-ring type seal 76 of suitable fuel-resistantelastomeric material is disposed in the groove of section 74 c.

[0036] Seat element 66 comprises an inwardly directed shoulder 66A thatcontains a portion of a through-hole that extends axially through theseat element. This portion of the through-hole comprises a straightcylindrical section 78 and a frustoconical seat surface 80 that extendsfrom the upper end of section 78 and is open to the interior spacebounded by neck 64. The remainder of the through-hole axially belowsection 78 is designated by the reference numeral 81.

[0037] The upper end of shaft 70 protrudes a distance above bushing 54and is shaped to provide for attachment of a spring seat 79 thereto.With piece B2 being attached to piece B1 by a clinch ring 82 which gripsconfronting, mated flanges to sandwich a seal 84 between them, a helicalcoiled linear compression spring 86 is captured between seat 79 andanother spring seat 87 that is received in a suitably shaped pocket ofpiece B2. A calibration screw 88 is threaded into a hole in the end wallof this pocket coaxial with axis AX, and it is externally accessible bya suitable turning tool (not shown) for setting the extent to whichspring seat 87 is positioned axially relative to the pocket.Increasingly threading screw 88 into the hole increasingly moves seat 87toward spring seat 79, increasingly compressing spring 86 in theprocess. Terminals 56 are also joined with terminals 90 mounted in pieceB2 to form an electrical connector 92 for mating engagement with anotherconnector (not shown) that connects to drive circuit 26.

[0038] In the valve closed position shown in FIG. 3, a rounded surfaceportion of seal 76 has circumferentially continuous sealing contact withseat surface 80 so that the valve closes the flow path between ports 14o′ and 14 i′. In this position the upper portion of armature 72 axiallyoverlaps the air gap that exists between the upper end of neck 62 andthe lower end of neck 58, but slight radial clearance exists so thatarmature 72 does not actually touch the necks, thereby avoiding magneticshorting.

[0039] Generally speaking, the degree of valve opening depends on themagnitude of electric current flow through the solenoid coil 46 so thatthe purge flow through the valve is effectively controlled bycontrolling the electric current flow through the coil. As the magnitudeof electric current flow progressively increases from zero, it reaches avalue sufficient to break whatever stiction exists between the seatedO-ring 76 and seat surface 80. At that point the valve mechanism beginsto open against the opposing force of spring 86. Valve opening commencesas soon as O-ring seal 76 loses contact with seat surface 80.

[0040] Depending on the specific geometric relationships that arepresent between the valve pintle, its O-ring seal, and the angle of thevalve seat surface, a certain initial axial travel of the pintle thatunseats O-ring seal 76 from seat surface 80 may have to occur beforetapered section 74B can become effective by itself to set the effectiveflow area through the seat element through-hole. In other words, it isonly after the valve has traveled more than some initial minimum traveldistance that the tapered section can become effective by itself tocontrol the area open to flow. Beyond this initial minimum, the openarea progressively uniformly increases as the pintle is increasinglypositioned away from the seat element.

[0041] A representative graph plot of fluid flow rate vs. electriccurrent reveals three distinct spans: a first span where currentincreases without any valve opening; a second span where the valvebegins to open but the tapered section 74B is not yet fully effective tocontrol the flow by itself; and a third span where the valve has openedsufficiently to allow section 74B to alone control the flow. The secondspan may be characterized by a relationship wherein a small incrementalchange in average electric current in solenoid S causes an incrementalchange in fluid flow rate that is substantially different from theincremental change results when the valve operates instead within thethird span.

[0042] Coil 46 of solenoid S is connected across a source of D.C.voltage pulses, such as a pulse-width modulator circuit operating at aselected frequency. Electric current flow to the coil may be controlledby a solid-state driver in accordance with a control output signal froman engine management computer, and the circuit may include a feedbackloop for feeding back a signal representative of electric current flowthrough the solenoid coil so as to endow the control with the ability tocompensate for certain environmentally induced changes that couldotherwise impair control accuracy. For example, the feedback loop canautomatically regulate the current flow through coil 46 such that theinfluences of changes in ambient conditions, such as temperature andD.C. supply voltage to the circuit, are essentially negated, therebyenabling the valve to operate to a desired position commanded by thecircuit substantially free of such influences.

[0043]FIG. 4 shows a mechanical pressure regulator 200 opperativelyassociated with valve 14′. Pressure regulator 200 comprises a two-piecebody 202 having a base 202 b and a cover 202 c, both of which arefabricated from suitable material, such as fuel tolerant injectionmolded plastic. Base 202 b comprises an inlet port 204 and an outletport 206 each of which is in the form of a nipple. A conduit 208 fluidconnects port 204 with outlet port 14 o′ of valve 14′, and outlet port206 is fluid connected with engine intake manifold by another conduitthat is not specifically illustrated in the Fig.

[0044] The nipple forming outlet port 206 comprises a walled conduithaving a radial segment that extends inwardly of body 202 to form anaxial segment that is coaxial with an axis 210 of pressure regulator200. This walled axial conduit segment terminates as a circular rimforming a seal seat 212. Base 202 b further comprises a cylindricalwalled cup having a circular annular radial shoulder 214. This cupterminates in a circular rim 216 that is coaxial with axis 210.

[0045] Cover 202 c has a generally circular shape whose outer peripherycontains one or more catches 218 that attach the cover to the otherwiseopen end of the cup of base 202 b at rim 216 by snapping over a lip ofthe rim as shown. The beaded outer circular perimeter of an impermeableflexible member 220 is held captured between the outer margin of cover202 c and rim 216 in a sealed manner. Centered with member 220 coaxialwith axis 210 is a rigid circular disk 222. Secured centrally to disk222 in confrontational juxtaposition to rim 216 is a circular sealelement 224. In the illustrated embodiment, element 224 is secured todisk 222 by being molded onto the disk, with a portion of the moldedmaterial passing from the element, through a small hole in the center ofthe disk, to create an interlocking circular formation 226 on theopposite face of the disk.

[0046] It can be seen that the outer margin of disk 222 contains anannular area free of molded material. One end of a helical coiledcompression spring 228 bears against this annular area. The opposite endof the spring bears against a wall of base 202 b that extendscircumferentially partially around the axial segment of the outlet portnipple below rim 212.

[0047] Cover 202 c is formed with a central depression 230, and in thecondition shown by FIG. 4, spring 228 is seen forcing disk 222 away fromrim 212 such that the flat end surface of formation 226 is biasedagainst the flat end surface of depression 230.

[0048] The assembled parts 220, 222, 224 form a fluid impermeable wall232 that divides the interior of body 202 into first and second chamberspaces 234, 236. In the position shown by the Fig., chamber 236 providesfree communication between ports 204 and 206. The flow path thusprovided is depicted by the arrows which represent purge flow from valve14′, through inlet port 202, through chamber space 236, and throughoutlet port 204 to the engine intake manifold. Chamber space 234 iscommunicated directly to atmosphere through an atmospheric vent orifice238 through the wall of cover 202 c.

[0049] Pressure regulator 200 operates in the following manner. Forpurposes of explanation, assume that it is in the position illustratedin the Fig., that equal pneumatic pressures exist in the two chamberspaces 234, 236, and that valve 14′ is open. The creation of increasingintake manifold vacuum in chamber space 236 will begin to create anincreasing pressure differential on wall 232. At a certain differential,the bias force of spring begins to be overcome, and the central regionof wall 232 begins moving toward rim 212. Atmospheric pressure ismaintained in chamber space 234 because air is drawn through ventorifice 238 as wall 232 moves toward rim 212. When the vacuum hasincreased to a certain larger magnitude, seal element 224 will besufficiently close to rim 212 to create a restriction of the purge flow.The seal element may actually close on rim 212, albeit only momentarily.Such restriction or closure, tends to reduce the pneumatic pressuredifferential acting on wall 232 so that spring 228 then tends to movethe central region of the wall away from rim 212. Atmospheric pressureis maintained in chamber space 234 because air is forced out throughvent orifice 238.

[0050] The overall effect is such that sealing element 224 will assumean average position that causes the vacuum in chamber space 236 to beregulated to a predetermined magnitude that is substantially independentof the magnitude of intake manifold vacuum. Hence, with the tankheadspace at atmospheric pressure, flow through the valve is essentiallyunaffected by change in intake manifold vacuum because a substantiallyconstant pressure differential is maintained across valve 14′. Now asvalve 14′ operates to different positions as commanded by the signalapplied to solenoid S, the commanded positions will producesubstantially the correspondingly intended purge flow rate,substantially free of variation in intake manifold vacuum. Becauseflexible member 220 is provided with a convolution, it imposes norestriction of the movement of the central region of the movable wallrelative to the open end of the walled axial conduit segment thatcontains rim 212.

[0051] Thus, in distinction to prior uses of pressure regulators inconjunction with pulsating purge valves, the disclosed embodiment doesnot utilize a pressure regulator for the purpose of dampening purge flowpulsations. Rather, the creation of a predetermined pressuredifferential acting across valve 14′ enables a given command signal todirectly provide the intended flow rate, free of manifold vacuumvariations. It is believed that this can eliminate the need for theengine management computer to include a map for processing an inputrepresenting intake manifold vacuum when it calculates what the commandsignal to the solenoid coil of the valve should be.

[0052]FIG. 5 shows a series of representative graph plots of purge flowrate through valve 14′ vs. time-averaged D.C. current flow in thesolenoid coil. Each graph plot corresponds to a different value ofintake manifold vacuum as indicated in FIG. 5, but the important effectof pressure regulator 200 can be seen by the substantial congruence ofgraph plots for 200, 300, 400, 500, and 600 mm Hg intake manifoldvacuum. In the examples of FIG. 5, purge flow commences at about 183milliamps current for the substantially congruent plots.

[0053]FIGS. 6 and 7 illustrate another embodiment in which an LSPV and apressure regulator are integrated into a single assembly. Like referencenumerals from the preceding Figs. are used to identify like parts,although from comparison of it can be seen that certain parts differ incertain details of construction. FIGS. 6 and 7 show that pressureregulator 200 has been integrated into the lower end of LSPV 14′. Thenipples that formed valve outlet port 14 o′ and regulator inlet port 208have been eliminated. The portion of the flow path downstream of thevalve pintle is communicated to chamber space 236 directly within thebody of the assembly.

[0054] Flexible member 220, seal element 224, and formation 226 areembodied as a single part that is created by insert molding onto disk222. The central region of cover 202 c comprises a tower 230′ which issomewhat different from the depression 230 of the earlier embodiment.Tower 230′ comprises a generally cylindrical wall 230 w having ashoulder 230 s. An orifice member 238 m is secured in place on cover 202c by a short axial wall 238 w that is press-fit to a portion of wall 230w. A circular radial flange 238 f at one axial end of wall 238 w isdisposed against shoulder 230 s to axially locate orifice member 238 mon cover 202 c.

[0055] One face of disk 222 comprises several circumferentially spacedformations 222 a that are arranged in a circular pattern to center oneaxial end of spring 228 against disk 222. The opposite disk facecomprises several circumferentially spaced formations 222 b alsoarranged in a circular formation. Proximate shoulder 230 s, cover 202 ccomprises a circular ridge 202 r against which formations 222 b bearwhen spring 228 is biasing seal element 224 maximally away from rim 212.

[0056] Orifice member 238 m contains a central through-orifice 238 othat corresponds to orifice 238 for communicating chamber space 234 toatmosphere through the interior of tower 230′ to openings 202 o thatextend through the wall of the tower. Pressure regulator 200 and valve14′ of the FIGS. 6 and 7 embodiment function in the same manner asdescribed above for the earlier embodiment.

[0057] While the solenoid S shown in FIG. 6 functions in the same manneras the solenoid shown in FIGS. 3 and 4, it differs in certainconstructional respects. The coil-containing bobbin 44, 46 and statorparts 48 and 52 are encased in an overmolding 300 to form an assemblagethat also includes the body part B2 as part of the overmolding.

[0058] Thus, the overmolding includes features forming the shell ofconnector 92 and accommodations for acceptance of spring 86 and itsassociated adjustment mechanism.

[0059] These parts that are to be overmolded are placed in a suitablyshaped mold cavity in a machine that forms the overmold around them. Asovermold material flows, it passes through holes in flanges of statorparts 48 and 52, covering the end surfaces and outer edges of the bobbinflanges and covering the exterior of coil 46. The two stator parts aresealed relative to the central interior through-hole of bobbin 44 suchthat the overmold material does not intrude into that through-hole. Uponcuring of the overmold material, the overmold has a final shape asshown, including a short neck at one end. The neck contains a circulargroove for acceptance of an O-ring 302 that, when the overmoldedassemblage is assembled into the valve during the fabrication process,serves to seal that end of the overmold to the wall of a single moldedplastic part 304 in which valve body part B1, base 202 b, and thenipples forming inlet port 14 i′ and exit 206 are integrated.

[0060] In the particular embodiment of FIG. 6, stator part 50 is notpart of the overmold assemblage. Rather, it is a separate tubular walledcylinder that is placed inside a main cylindrical wall 305 of body partB1 via the open upper end thereof, as seen in FIG. 6, and it is axiallycaptured therein by the overmold assemblage as the latter is inserted toassembled position within space bounded by wall 305.

[0061] The overmold assemblage is retained in final assembled positionshown in FIG. 6 by several catches 306 on the wall of part 304 that snapover radial protrusions 307 extending from the overmold. Prior toinsertion of the overmold assemblage into the space bounded by wall 305,various internal parts such as 54, 60, 70, 72, 79, 86, 87, 88 areassembled into the overmold assemblage. Also, the valve seat element 66is assembled to part 304, that element having a cylindrical wall fittedin a sealed manner by an O-ring 308 to the open internal end (co-axialwith axis AX) of the nipple that forms inlet port 14 i′. Above itstransverse wall that contains the valve through-hole controlled by valve74, the valve seat element contains an apertured cylindrical wall thatprovides for vapor flow that has passed through the seat elementthrough-hole to flow to an internal space of part 304 and thence enterregulator chamber space 236. The vapor flow path is indicated by theunnumbered arrows in FIGS. 6 and 7.

[0062] Embodiments utilizing the inventive principles may be constructedin diverse ways. Because automotive electronic technology commonlyemploys electronic processors, the development of the electric controlsignal for the solenoid may be accomplished by utilizing conventionalsoftware programming techniques to develop the desired waveform orwaveforms for any specific control strategy.

[0063] While the present invention has been described with reference toa preferred embodiment as currently contemplated, it should beunderstood that the invention is not intended to be limited to thatembodiment. Accordingly, the invention is intended to encompass variousmodifications and arrangements that are within the scope of the claims.

What is claimed is:
 1. An electric-operated pressure-regulated fluidflow control valve comprising a valve mechanism that is positionedwithin a valve body by an electric control signal to control fluid flowthrough the valve body and that has a frequency response characteristicwhich renders the valve mechanism incapable of faithfully tracking thefundamental frequency of an electric control signal whose fundamentalfrequency is greater than a predetermined frequency that, when appliedin control of the valve mechanism, positions the valve mechanism to aposition corresponding to a most recent time average of the electriccontrol signal free of any significant pulsing of the valve mechanism,and a pressure regulator comprising a flow path having an entrancethrough which fluid flow that has passed through the valve mechanismenters the pressure regulator flow path and an exit from which fluidflow that has entered the pressure regulator flow path exits thepressure regulator flow path, said pressure regulator comprising apressure regulating mechanism that regulates the pressure at theentrance of the pressure regulator flow path to a pressure that isessentially independent of pressure at the exit of the pressureregulator flow path.
 2. A fluid flow control valve as set forth in claim1 wherein said pressure regulator comprises a body enclosing an interiorspace, and said pressure regulating mechanism comprises a movable walldividing the interior space into a first chamber space and a secondchamber space, said second chamber space forming a portion of thepressure regulator flow path, and said first chamber space beingcommunicated to a reference pressure.
 3. A fluid flow control valve asset forth in claim 2 wherein said reference pressure is ambientatmospheric pressure.
 4. A fluid flow control valve as set forth inclaim 2 wherein the exit of said pressure regulator flow path iscommunicated to a variable vacuum.
 5. A fluid flow control valve as setforth in claim 2 wherein said pressure regulator entrance comprises anexternal nipple, and further including a conduit fitted to said nippleto convey fluid from the valve body to the nipple.
 6. A fluid flowcontrol valve as set forth in claim 2 wherein the valve body and thepressure regulator body are assembled together to form an enclosurethrough which fluid flow passes from the valve mechanism to the pressureregulating mechanism.
 7. A fluid flow control valve as set forth inclaim 1 wherein said pressure regulating mechanism comprises a movablewall separating a variable volume first chamber space from a variablevolume second chamber space, said second chamber space forming a portionof the pressure regulator flow path, and said first chamber space beingcommunicated to a reference pressure.
 8. A fluid flow control valve asset forth in claim 7 wherein said movable wall comprises a rigid diskdisposed centrally on said movable wall and a flexible membercircumscribing said disk, and further including a seal element disposedcentrally on said disk.
 9. A fluid flow control valve as set forth inclaim 8 wherein said pressure regulating mechanism includes a helicalcoiled spring having one axial end bearing against said disk andcircumscribing said seal element.
 10. A fluid flow control valve as setforth in claim 8 wherein said helical coiled spring and said sealelement are disposed in said second chamber space.
 11. A fluid flowcontrol valve as set forth in claim 7 wherein said pressure regulatorfurther comprises a walled conduit having an open end disposed in thesecond chamber space in juxtaposition to a central region of the movablewall and leading to the pressure regulator flow path exit, the movablewall further comprising a flexible convoluted member circumscribing thecentral region of the movable wall to allow unrestricted movement of thecentral region relative to the open end of the walled conduit.
 12. Afluid flow control valve as set forth in claim 11 wherein said pressureregulating mechanism includes a spring bearing against the centralregion of the movable wall and urging the central region of the movablewall away from the open end of the walled conduit.
 13. A fluid flowcontrol valve as set forth in claim 12 wherein said spring comprises ahelical coiled spring having an axial end bearing against the centralregion of the movable wall, said spring being disposed in said secondchamber space.
 14. A-fluid flow control valve as set forth in claim 13wherein the central region of the movable wall comprises a rigid diskagainst which the axial end of the spring bears.
 15. A fluid flowcontrol valve as set forth in claim 14 wherein the central region of themovable wall comprises a seal element disposed on a central region ofthe rigid disk in juxtaposition to the open end of the walled conduitand circumscribed by the axial end of the spring.
 16. A fluid flowcontrol valve as set forth in claim 1 wherein the valve mechanismcomprises a linear solenoid actuator to which the electric controlsignal is applied.
 17. A fluid flow control valve as set forth in claim16 wherein the linear solenoid actuator comprises a bobbin, a coil onthe bobbin to which the electric control signal is applied, statorstructure associated with the coil, and an overmold joining the bobbinand the stator structure in assembly and covering the coil.
 18. A fluidflow control valve as set forth in claim 16 further including anelectric control circuit that applies the electric signal to the linearsolenoid actuator at a fundamental frequency substantially greater thanthe frequency response characteristic of the valve mechanism.
 19. Anelectric-operated pressure-regulated fuel vapor purge valve for purgingfuel vapor from a fuel tank to an intake manifold of an internalcombustion engine comprising a valve mechanism that is positioned withina valve body by an electric control signal to control flow through thevalve body and that has a frequency response characteristic whichrenders the valve mechanism incapable of faithfully tracking thefundamental frequency of an electric control signal whose fundamentalfrequency is greater than a predetermined frequency that, when appliedin control of the valve mechanism, positions the valve mechanism to aposition corresponding to a most recent time average of the electriccontrol signal free of any significant pulsing of the valve mechanism,and a pressure regulator comprising a flow path having an entrancethrough which flow that has passed through the valve mechanism entersthe pressure regulator flow path and an exit for communicating thepressure regulator flow path to an engine intake manifold, said pressureregulator comprising a pressure regulating mechanism that regulates thepressure at the entrance of the pressure regulator flow path to apressure that is essentially independent of intake manifold vacuum. 20.A fuel vapor purge valve as set forth in claim 19 wherein said pressureregulator comprises a body enclosing an interior space, and saidpressure regulating mechanism comprises a movable wall dividing theinterior space into a first chamber space and a second chamber space,said second chamber space forming a portion of the pressure regulatorflow path, and said first chamber space being communicated to areference pressure.
 21. A fuel vapor purge valve as set forth in claim20 wherein said reference pressure is ambient atmospheric pressure. 22.A fuel vapor purge valve as set forth in claim 20 wherein said pressureregulator entrance comprises an external nipple, and further including aconduit fitted to said nipple to convey flow from the valve body to thenipple.
 23. A fuel vapor purge valve as set forth in claim 20 whereinthe valve body and the pressure regulator body are assembled together toform an enclosure through which flow passes from the valve mechanism tothe pressure regulating mechanism.
 24. A fuel vapor purge valve as setforth in claim 19 wherein said pressure regulating mechanism comprises amovable wall separating a variable volume first chamber space from avariable volume second chamber space, said second chamber space forminga portion of the pressure regulator flow path, and said first chamberspace being communicated to a reference pressure.
 25. A fuel vapor purgevalve as set forth in claim 24 wherein said movable wall comprises arigid disk disposed centrally on said movable wall and a flexible membercircumscribing said disk, and further including a seal element disposedcentrally on said disk.
 26. A fuel vapor purge valve as set forth inclaim 25 wherein said pressure regulating mechanism includes a helicalcoiled spring having one axial end bearing against said disk andcircumscribing said seal element.
 27. A fuel vapor purge valve as setforth in claim 26 wherein said helical coiled spring and said sealelement are disposed in said second chamber space.
 28. A fuel vaporpurge valve as set forth in claim 24 wherein said pressure regulatorfurther comprises a walled conduit having an open end disposed in thesecond chamber space in juxtaposition to a central region of the movablewall and leading to the pressure regulator flow path exit, the movablewall further comprising a flexible convoluted member circumscribing thecentral region of the movable wall to allow unrestricted movement of thecentral region relative to the open end of the walled conduit.
 29. Afuel vapor purge valve as set forth in claim 28 wherein said pressureregulating mechanism includes a spring bearing against the centralregion of the movable wall and urging the central region of the movablewall away from the open end of the walled conduit.
 30. A fuel vaporpurge valve as set forth in claim 29 wherein said spring comprises ahelical coiled spring having an axial end bearing against the centralregion of the movable wall, said spring being disposed in said secondchamber space.
 31. A fuel vapor purge valve as set forth in claim 30wherein the central region of the movable wall comprises a rigid diskagainst which the axial end of the spring bears.
 32. A fuel vapor purgevalve as set forth in claim 31 wherein the central region of the movablewall comprises a seal element disposed on a central region of the rigiddisk in juxtaposition to the open end of the walled conduit andcircumscribed by the axial end of the spring.
 33. A fuel vapor purgevalve as set forth in claim 19 wherein the valve mechanism comprises alinear solenoid actuator to which the electric control signal isapplied.
 34. A fuel vapor purge valve as set forth in claim 33 whereinthe linear solenoid actuator comprises a bobbin, a coil on the bobbin towhich the electric control signal is applied, stator structureassociated with the coil, and an overmold joining the bobbin and thestator structure in assembly and covering the coil.
 35. A fuel vaporpurge valve as set forth in claim 34 further including an electriccontrol circuit that applies the electric signal to the linear solenoidactuator at a fundamental frequency substantially greater than thefrequency response characteristic of the valve mechanism.